1. Field of the Invention
This invention relates to a base for a coating material made of synthetic resin.
2. Description of the Prior Art
Conventionally, in the execution of a plastic flooring, the floor for example, may be finished by applying a coating material (flooring material) made of liquid synthetic resin such as urethane, epoxy or the like directly to a floor base made of concrete, i.e., concrete base. A film or layer of the coating material is successively hardened from its outer surface thereof contacting the air toward its back contacting the concrete base with the passage of time to form a floor surface.
Now, it has been pointed out that the film or layer of the coating material directly applied to the concrete base often produce defects such as pinholes opening to the surface of the film and blisters swelled up on the surface.
The defects have been considered to be caused by the fact that gas generated in the interior of the film or layer while the film or layer is hardening may be emitted to the atmosphere only from the surface of the film or layer.
Since a gas has the specific gravity smaller than that of the coating material constituting the film or layer, it tends to move through the film or layer toward the surface thereof. Accordingly, the gas is emitted from the surface of the film or layer to the atmosphere while the surface is relatively soft, i.e., has fluidity. However, when the surface is hardened with the passage of time to make the emission of the gas from the surface difficult, the gas moves toward the back which hardens later than the surface. This gas accordingly increases the internal pressure in the film or layer. However, since the back contacts the concrete base, the gas is not emitted to the atmosphere so that the internal pressure of the gas is further increased with the passage of time. The film or layer is exfoliated from the concrete due to the increase of the internal pressure to bring about the swelling phenomenon of blistering. Further, the gas having the increased internal pressure is forced to pass through the film or layer and slips out of the surface which has almost lost its fluidity, thereby leaving pinholes after the gas slips out of the surface.